crypto: simplify Context encoding (#11812)

This commit adds a `MarshalText` implementation
to the `crypto.Context` type.
The `MarshalText` implementation replaces the
`WriteTo` and `AppendTo` implementation.

It is slightly slower than the `AppendTo` implementation
```
goos: darwin
goarch: arm64
pkg: github.com/minio/minio/cmd/crypto
BenchmarkContext_AppendTo/0-elems-8         	381475698	         2.892 ns/op	       0 B/op	       0 allocs/op
BenchmarkContext_AppendTo/1-elems-8         	17945088	        67.54 ns/op	       0 B/op	       0 allocs/op
BenchmarkContext_AppendTo/3-elems-8         	 5431770	       221.2 ns/op	      72 B/op	       2 allocs/op
BenchmarkContext_AppendTo/4-elems-8         	 3430684	       346.7 ns/op	      88 B/op	       2 allocs/op
```
vs.
```
BenchmarkContext/0-elems-8         	135819834	         8.658 ns/op	       2 B/op	       1 allocs/op
BenchmarkContext/1-elems-8         	13326243	        89.20 ns/op	     128 B/op	       1 allocs/op
BenchmarkContext/3-elems-8         	 4935301	       243.1 ns/op	     200 B/op	       3 allocs/op
BenchmarkContext/4-elems-8         	 2792142	       428.2 ns/op	     504 B/op	       4 allocs/op
goos: darwin
```

However, the `AppendTo` benchmark used a pre-allocated buffer. While
this improves its performance it does not match the actual usage of
`crypto.Context` which is passed to a `KMS` and always encoded into
a newly allocated buffer.

Therefore, this change seems acceptable since it should not impact the
actual performance but reduces the overall code for Context marshaling.
This commit is contained in:
Andreas Auernhammer
2021-03-20 10:48:48 +01:00
committed by GitHub
parent 9a6487319a
commit 7b3719c17b
5 changed files with 57 additions and 132 deletions
+8 -28
View File
@@ -223,7 +223,10 @@ func (v *vaultService) CreateKey(keyID string) error {
// named key referenced by keyID. It also binds the generated key
// cryptographically to the provided context.
func (v *vaultService) GenerateKey(keyID string, ctx Context) (key [32]byte, sealedKey []byte, err error) {
context := ctx.AppendTo(make([]byte, 0, 128))
context, err := ctx.MarshalText()
if err != nil {
return key, sealedKey, err
}
payload := map[string]interface{}{
"context": base64.StdEncoding.EncodeToString(context),
@@ -258,7 +261,10 @@ func (v *vaultService) GenerateKey(keyID string, ctx Context) (key [32]byte, sea
// The context must be same context as the one provided while
// generating the plaintext key / sealedKey.
func (v *vaultService) UnsealKey(keyID string, sealedKey []byte, ctx Context) (key [32]byte, err error) {
context := ctx.AppendTo(make([]byte, 0, 128))
context, err := ctx.MarshalText()
if err != nil {
return key, err
}
payload := map[string]interface{}{
"ciphertext": string(sealedKey),
@@ -282,29 +288,3 @@ func (v *vaultService) UnsealKey(keyID string, sealedKey []byte, ctx Context) (k
copy(key[:], plainKey)
return key, nil
}
// UpdateKey re-wraps the sealedKey if the master key referenced by the keyID
// has been changed by the KMS operator - i.e. the master key has been rotated.
// If the master key hasn't changed since the sealedKey has been created / updated
// it may return the same sealedKey as rotatedKey.
//
// The context must be same context as the one provided while
// generating the plaintext key / sealedKey.
func (v *vaultService) UpdateKey(keyID string, sealedKey []byte, ctx Context) (rotatedKey []byte, err error) {
context := ctx.AppendTo(make([]byte, 0, 128))
payload := map[string]interface{}{
"ciphertext": string(sealedKey),
"context": base64.StdEncoding.EncodeToString(context),
}
s, err := v.client.Logical().Write(fmt.Sprintf("/transit/rewrap/%s", keyID), payload)
if err != nil {
return nil, Errorf("crypto: client error %w", err)
}
ciphertext, ok := s.Data["ciphertext"]
if !ok {
return nil, errMissingUpdatedKey
}
rotatedKey = []byte(ciphertext.(string))
return rotatedKey, nil
}